CA1249036A - Microwave ovens and methods of cooking food - Google Patents
Microwave ovens and methods of cooking foodInfo
- Publication number
- CA1249036A CA1249036A CA000498944A CA498944A CA1249036A CA 1249036 A CA1249036 A CA 1249036A CA 000498944 A CA000498944 A CA 000498944A CA 498944 A CA498944 A CA 498944A CA 1249036 A CA1249036 A CA 1249036A
- Authority
- CA
- Canada
- Prior art keywords
- cooking
- microwave
- temperature
- power
- hot air
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000010411 cooking Methods 0.000 title claims abstract description 74
- 238000000034 method Methods 0.000 title claims abstract description 32
- 235000013305 food Nutrition 0.000 title abstract description 14
- 235000013372 meat Nutrition 0.000 claims abstract description 19
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 244000144977 poultry Species 0.000 claims description 25
- 230000002045 lasting effect Effects 0.000 claims description 2
- 238000001514 detection method Methods 0.000 abstract 1
- 235000020989 red meat Nutrition 0.000 description 4
- 230000001419 dependent effect Effects 0.000 description 3
- 235000013611 frozen food Nutrition 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 2
- 235000012054 meals Nutrition 0.000 description 2
- 241000272470 Circus Species 0.000 description 1
- 241001269524 Dura Species 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 235000014594 pastries Nutrition 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/6435—Aspects relating to the user interface of the microwave heating apparatus
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/6447—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
- H05B6/645—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using temperature sensors
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/647—Aspects related to microwave heating combined with other heating techniques
- H05B6/6473—Aspects related to microwave heating combined with other heating techniques combined with convection heating
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/647—Aspects related to microwave heating combined with other heating techniques
- H05B6/6482—Aspects related to microwave heating combined with other heating techniques combined with radiant heating, e.g. infrared heating
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Human Computer Interaction (AREA)
- Electric Ovens (AREA)
- Control Of High-Frequency Heating Circuits (AREA)
Abstract
Abstract Title: Microwave Ovens and Methods of Cooking Food A microwave oven has a magnetron for producing microwave power and a resistance heating element over which air is forced by a fan to produce a forced flow of hot air through the oven cavity. A thermistor in the hot air flow senses the temperature of the hot air. Microwave power and hot air are produced simultaneously until the sensed hot air temperature reaches a predetermined threshold temperature (Tl). For baked food items this represents the end of the cooking process, but for meat items there is a final cooking stage during which no hot air is forced through the cavity, the level of microwave power being doubled during the final stage. The end of the final stage occurs when the sensed temperature drops to a predetermined threshold (TS) . The absence of forced hot air during the final stage makes the detection of the predetermined threshold temperature (TS) easier, because the slope of the hot air temperature/time curve is steeper than would be the case if hot air were produced to the end of the cooking process.
Description
C304.5/M
Title: Microwave Ovens and Methods of cooking food Field of the Invention This invention relates to microwave ovens and to methods Oe coo~ing food.
Backqround to the Invention The applicants' European Patent Specification No 0122710 discloses a microwave oven which delivers microwave power to the oven cavity simultaneously with thermal power provided by a circu~lation of hot air forGed through the cavity by a fan. A temperature sensor ~sensing temperature of the hot air) and a timing means monitor the temperature/time variation. If a predetermined maximum temperature (eg 250~C~ of the hot air is reached in a predetermined time (eg 30 minutes) from commencement of cooking with the oven in a cold conditionj the oven automatically switches off to inish the cooking process.
Most food items other than large meat or casserole dishes will be cooked within the predetermined time by this method. For larger meat and casserole dishes, where the maximum temperature is reached after the predetermined time, the delivery of microwave power is increased and the delivery of thermal power is decreased when the maximum temperature is reached in order to complete cooking of these denser food items. For such denser food items, the hot air temperature decreases with time after the predetermined time has elapsed, but the curve has a small ~a , ...... ... ... ~ .............
(negative) slope which means that inaccuracies can arise if the end of cooking is determined by the temperature dropping to any set level.
The present invention relates to a modified way of cooking such denser food items which do not reach the predetermined maximum temperature within the predetermined time, the aim of the modification being to increase the slope of the temperature/time curve during the final stage of cooking to make switch-off more precise in time.
Summary of the Invention According to the invention there is provided a microwave oven comprising a microwave generator for supplying microwave power to a cavity of the oven, thermal heating means for supplying thermal power in the form of a forced flow of hot air through the cavity, memory means storing a irst cooking program appropriate to a baked item, a second cooking program appropriate to a meat joint other than poultry, and a third cooking program appropriate to poultry, selector means for selecting one of said first, second and third cooking programs, temperature sensing means for sensing the temperature of the hot air flow, and control means which are responsive to the selector means and the te~perature sensing means and which, when the sensed temperature reaches a predetermined level due to the simultaneous generation of microwave power and thermal power, are operative either to switch off the supply of power to the microwave generator and the thermal heating means and thereby finish the cooking process if the first G,~ 3~i program has been selected or if the second or third program has been selectedr are operat.ive to finish the cooking process by the application of microwave power w.ithout any application of thermal power during a final cooking stage, un-til the sensed temperature drops to a predetermined switch ofE temperature which is lower than the predetermined temperature level and at which the supply of microwave power ceases.
When cooking poultry, the final stage preferably commences lo when the sensed temperature reaches the predetermined level and finishes when the sensed temperature reaches the predetermined switch off temperature. During the final stage the microwave power is preferably increased cornpared with the level of microwave power generated pr.ior to the sensed temperature reaching the predetermined level.
Preferably, the microwave power level is doubled when the 3~
sensed temperature reaches the predetermined level, the supply of thermal power also being discontinued at this point so that no hot air is produced during the final cooking stage.
The temperature sensing means preferably sense the temperature of the hot air flow at a position just downstream of an electric resistance heating element over which the air is recirculated by a fan.
When cooking meats other than poultry, there is preferably an intermediate stage commencing when the sensed temperature reaches the predetermined level and lasting until the sensed temperature 3rops to an intermediate threshold when the final stage commences. During the intermediate stage, the amount of thermal power is preferably reduced, and the amount of microwave power is preferably increased, compared with the respective power levels obtaining prior t~ the sensed temperature reaching the predetermined level.
When cooking poultry items the sensed temperature wlll take longer to reach the predetermined level than for meat items excluding poultry. This time difference can be used to advantage as the temperature/time variation detected by the oven can be used to sense whether the item being cooked is a pouItry item or a meat item other than poultry. If the temperature/time variation indicates that a poultry item is being cooked, when the sensed temperature reaches the predetermined level the oven switches immediately into the final cooking stage during which no hot air is produced. Alternatively, if the temperature/time ~ariation indicates that a meat item other than poultry i9 being cooked, then the oven 3~
commences the intermediate stage when the sensed temperature reaches the predetermined level, and commences the final cooking stage when the sensed temperature reaches the intermediate threshold.
Preferably the oven has the facility to prolong the cooking process for a predetermined proportion of the time occupied by the cooking process, the prolongation being at the levels of microwave power and thermal power prevailing at the switch-off time. Said predetermined proportion may 10 be between 15% and 25%, preferably about 20~.
According to a yet further aspect of the invention there is provided a method of cooking a red meat or poultry item in a microwave oven, comprising commencing with a cavity of the oven in a cold condition, simultaneously applying 15 microwave power and thermal power in the form of a forced flow of hot air through the oven cavity until the hot air temperature reaches a predetermined level, after which the cooking process is finished by the application of microwave power without any thermal power during a final 20 cooking stage, un~il the hot air temperature drops to a predetermined switch-off temperature at which the supply of microwave power ceases.
The invention will now be further described by way of éxample with reference to the accompanying drawings in 25 which: ~
.
Figure 1 is a temperatur'e/time graph showing the variation of hot air temperature with time for a meat item other than poultry cooked ijn a first microwave oven capable of coo~ing in an automatic mode, 3~
Figure 2 i~ a graph corresponding to Figure 1 but showing the temperature/time variation for a poultry item, Fiqure 3 shows the control panel of the second 5 microwave oven capable of cooking in a semi-automatic mode, Figure 4 is a graph showing the temperature/time variations for differing foods cooked in the second microwave oven, Figures 5a and Sb are together a flow chart depicting the cooking process for a baked item of food cooked in the second microwave oven, and Figures 6a to lOa are flow charts depicting the first parts of ~ooking processes of five differing foodstuffs 15 cooked in the second microwave oven.
:
The~ first microwave oven acccrding to the invention is similar to that described in the applicants' European patent application No 0122710 r except that the control means governing the operation of the microwave power and 20 the thermal power are modified so that meats other than poultry are cooked according to the graph of Figure 1 and poultry items are cooked according to the graph of Figure j 2. ~ood items other than meats are cooked in the manner I ~ desoribed in the referenced European patent application.
-25 The Gven has temperature sensing means which comprise a thermistor positioned in the hot air stream just downstream of an~ electric resistance heatinq element. The electric resistance element i5 positioned in a compartment , .
3~
behlnd the back wall of the oven cavity~ as described in the referenced European patent application.
Referring to Figure 1, a meat item other than poultry is subjected to simultaneous microwave power and forced hot 5 air during an initial stage 10 during which the sensed temperature rises steadily with time. When the sensed temperature reaches a predetermined level T1 the m;crowave power level is doubled and the thermal power level is halved for an intermediate stage 12 during which the hot 13 air temperature declines until it reaches a predetermined intermediate threshold temperature level T2. At temperature T2, a final cooking stage 14 commences. During the final cooking stage 14 the microwave power level is maintained at its doubled value but no thermal power is 15 produced. The temperature/time variation therefore drops more steeply during this final cooking stage 14 . When the sensed temperature reaches a predetermined switch off temperature TS, the production of microwave power ceases to mark the end of the cooking process at the time ts.
20 The steepnes of the curve in the final cooking stage 14 provides a precise cut off point at the switch off temperature TS.
During the initial stage 10, the power level may be 200 watts microwave power into the cavity and 1130 watts of 25 hot air, and during the intermediate stage 12 the respective power levels may be 500 and 550 watts. nurin~
the final stage 14, the microwave power level remains at 500 watts but there is no hot air produced. Temperature Tl may be about 2S5QC and ~emperature T2 about 200C.
The temperature~time curve for a poultry item is shown in Figure 2. During the initial stage 10, microwave power and 3~
hot air power are applied simultaneousl~ to the oven cavity until the sensed temperature reaches the predetermined level Tl. This occurs at a time longer than that required for a meat item other than poultry to reach this predetermined temperature level Tl. When ~emperature Tl is reached, the microwave oven switches into its final cooking stage 14 during which the microwave power level is doubled but no hot air is produced. The temperature~ time curve during the final stage 14 therefore drops fairly steeply to provide a precise cut of at the predetermined switch off temperature TS when cooking ceases at time ts.
The power levels during stages 10 and 14 in Figure 2 correspond to the power levels in the stages 10 and 14 in Figure 1.
It will be appreciated that for poultry items and for meat items other than poultry the operation after the sensed temperature has reached the predetermined level Tl is governed by the falling off of the sensed temperature and not by time. As a result of producing no hot air during the final cooking stage 14, the temperature/time curve drops sharply to produce a precise cut off point at the predetermined switch of~ temperature TS.
The first embodiment of microwave oven ls capable of cooking in automatic mode, in that the user does not need to pre-select any particular cooking ~program. The cooking program actually followed in any particular case will be dependent on the temperature/time curve, and in particular the time when the threshold temperature Tl is reached, as described in the aforementioned European patent ~30 appll~catlon.~ ~ ~
Some users prefer to have more control` over the cooking :
3~i process, and the second microwave oven has been developed to meet this need. The second microwave oven is semi-automatic in operation,in that the user pre-selects a program appropriate to the type of food item being cooked, but the manner in which the selected program proceeds is dependent on the temperature/time variation.
Figure 3 shows the control panel of ~he se~ond oven. The panel has a display 20 depicting time and date, together with pads 22 for setting the time and date. Under the lO display 20 are a pad 24 depicted "Automatic Hi-Speed", a pad 26 depicted l'Manual Hi-Speed Turbo" and a pad 28 depicted "Microwave Cook/Defrost". On respective sides are pads 30, 32 marked "Down" and "Up". A large touch pad 34 marked "Start" is provided,and pads 36, 38 marked "Door Open" and "Reset/Off" complete the display panel.
The second oven is again similar in circuit components to that disclosed in the applicants' European patent application published under No 0122710 in that the microwave power i5 delivered to the oven cavity simultaneously with thermal power provided by a circulation of hot air forced through the cavity by a fan.
A temperature sensor in the hot air flow and timing means monitor the temperaturejtime variation. A microprocessor controls the magnitude and duration of the application of the microwave power, and the magnitude and dura~ion of the thermal~power, in~dependence upon temperature/time variatiln.
However, the oven is capable of following a selected one ~of six cooking programs appropriate to the foodstuff being cooked. For example, ie the user wishes to cook a baked foodstuff, eg a pastry item, the pad 24 is touched and ~$~
~ 10 --this causes the microprocessor to control the microwave power and the thermal power so that a cooking procedure appropriate to baked items is followed. The pad 24 is touched a second time if a frozen item is to he defrosted and cooked. The pad 24 is touched a third time if a red meat item is to be cooked, and the pad 24 is touched a fourth time if a poultry item is to be cooked. The pad 24 is touched a fifth time if a complete individual meal is to be cooked, and the pad 24 is touched a sixth time if a 10 pre-cooked food item is to be heated.
Once the pad 24 is touched the number of times appropriate to the foodstuff beir.g cooked, the oven performs the appropriate cooking procedure and terminates the cooking procedure at a switch-off time which will be dependent on 15 the temperature/time variation. If, at switch-off time, the food item is considered not to be cooked the user can again press the "Start" pad 34 which then serves as an 'extra-time' pad and automatically prolongs the cooking procedure for a further 20~ of the cooking time from 20 com~encement of cooking to switch-off time.
Pad 38 is a reset/cancel pad which is operative to cancel any previously selected cooking procedure entered in by pad 24. Pads 30 and 32 (marked "Down" and "Up") enable less well cooked or more well cooked results to be 25 achieved, respectively. For example, if the pad 24 is touched three times to select the red meat cooking progra~
and the pad 30 is touched, the meat item cooked will be rarer than if pad 30 had not ~een touched. Similarly, if pad 32 is touched instead of pad 30 the meat item will be 30 well done.
F~gure 4 shows the tewperature/time variations followed for typical cooking procedures in the second oven. Curve 40 is the temperature/time variation for a typical baked i~em consequent upon touchlrlg of the pad 24 once. The oven automatically switches off when a thrleshold temperature Tl is reached~ which occurs at time C. Curve 42 shows the temperature/time variation for a frozen item which is first defrosted and then cooked, cooking finishing when a predetermined temperature T3 is reached, which occurs at switch off time E. Curve 44 is the temperature/time 10 variation for red meats, cooking finishing at time H.
Curve 46 is the temperature/time variation for poultry, for which cooking finishes at time F. Curve 48 is for items which are being re-heated, which lasts until time A.
Curve 46 results from there being a final cooking stage lS like stage 14 of Figure 2, and curve 44 results fro~ there being an intermediate cooking stage and a final stage, corresponding to stages 12 and 14 of Figure l. It will be noted that curve 44 commences its intermediate stage at a lower temperature than does the curve 46 commence its 20 final stage, this being the only significant difference as between the automatic oven (Figures l and 2) and the semi-automatic oven (Figure 4).
In each case, if extra time is selected after the selected cookîng procedure has been completed r the microprocessor 25 remembers the last mode it was operating in and the overall time taken and automatically programs the oven to cook for a further 20~ of that time. Hence, ifia haked item is cooked and the oven switches off at time C of 20 minutes, subsequent selèctlon of extra time will cause the 30 oven to continue the cooking procedure for a further 4 minutes.
When the pad 24 is touched once, to select a program , ,,,, ,, ,,,_ ,, , ,,, . , .... ..... ..... , . , . . .. -- ---~ ., 3~
appropriate to a baked item, the second microwave oven follows a cooking procedure shown in the flow chart of Figures 5a and 5b. The part of the procedure shown at S0 is the selection of the 'baked' program, with the option for lightly baked or well baked, and the starting of cooking by touching the pad 340 If the temperature (as detected by the thermistor in the rear compartment~ is above 80C, automatic cool down of the oven cavity is achieved by directing cooling air through the oven cavity from the magne~ron blower and the convection blower, as indicated at 52.
As cooking proceedsr the total cooking time is monitored (54) and the display 20 shows the program selected and whether the Down or Up pad was touched. When the threshold temperature Tl is reached, the production of microwave power and convection power ceases ~56~, and the display 20 then shows "Cooking Complete" (58).
After the oven door has been opened, the display 20 invites the user to select the option of extra time. If this is required, the user again presses the start pad 34 (as indicated at 59j, and the oven automatically continues both microwave power and thermal power, at the levels prevailing immediately before switch off, for a further time equal to 20% of the time from commencement o~ cooking to switch Off-Yet further extra time may be selected (69) if the userwishes.
' During any extra time cooking, the display 20 shows 20% of the cooking time as monitored at 54, and the timer counts 30 ~own to ~ero.
, Figure 6a corresponds to Figure 5a, but shows the flow chart appropriate to the p~ogram for frozen foods. The remainder of the program for frozen foods is identical to that for baked items, so Figure 6a should be combined with 5 Figure 5b for the complete flow chart for frozen food items.
Similarly, Figure 7a corresponds to Figure 5a, but shows the flow chart appropriate to roast meats. It will be seen that the program has stages 1, 2 and 3 corresponding to 10 the curve 44 of Figure 4. The remainder of the program for roast meats is identical to that for baked items, so Figure 7a should be combined with Figure 5b for the complete flow chart for roast meat items.
Figure 8a corresponds to Figure 5a, but shows the flow 15 chart appropriate to poultry. It will be seen that the program has stages 1 and 3, corresponding to the curve 46 of Figure 4. The remainder of the program for poultry i5 identical to that for baked items. So Figure 8a should be combined with Figure 5b for the complete flow chart for 20 poaltry items.
Figures 9a and lOa correspond to Figure 5a, but show the flow charts appropriate to cooking complete individual meals and heating pre-cooked foo~s, respectively.
Title: Microwave Ovens and Methods of cooking food Field of the Invention This invention relates to microwave ovens and to methods Oe coo~ing food.
Backqround to the Invention The applicants' European Patent Specification No 0122710 discloses a microwave oven which delivers microwave power to the oven cavity simultaneously with thermal power provided by a circu~lation of hot air forGed through the cavity by a fan. A temperature sensor ~sensing temperature of the hot air) and a timing means monitor the temperature/time variation. If a predetermined maximum temperature (eg 250~C~ of the hot air is reached in a predetermined time (eg 30 minutes) from commencement of cooking with the oven in a cold conditionj the oven automatically switches off to inish the cooking process.
Most food items other than large meat or casserole dishes will be cooked within the predetermined time by this method. For larger meat and casserole dishes, where the maximum temperature is reached after the predetermined time, the delivery of microwave power is increased and the delivery of thermal power is decreased when the maximum temperature is reached in order to complete cooking of these denser food items. For such denser food items, the hot air temperature decreases with time after the predetermined time has elapsed, but the curve has a small ~a , ...... ... ... ~ .............
(negative) slope which means that inaccuracies can arise if the end of cooking is determined by the temperature dropping to any set level.
The present invention relates to a modified way of cooking such denser food items which do not reach the predetermined maximum temperature within the predetermined time, the aim of the modification being to increase the slope of the temperature/time curve during the final stage of cooking to make switch-off more precise in time.
Summary of the Invention According to the invention there is provided a microwave oven comprising a microwave generator for supplying microwave power to a cavity of the oven, thermal heating means for supplying thermal power in the form of a forced flow of hot air through the cavity, memory means storing a irst cooking program appropriate to a baked item, a second cooking program appropriate to a meat joint other than poultry, and a third cooking program appropriate to poultry, selector means for selecting one of said first, second and third cooking programs, temperature sensing means for sensing the temperature of the hot air flow, and control means which are responsive to the selector means and the te~perature sensing means and which, when the sensed temperature reaches a predetermined level due to the simultaneous generation of microwave power and thermal power, are operative either to switch off the supply of power to the microwave generator and the thermal heating means and thereby finish the cooking process if the first G,~ 3~i program has been selected or if the second or third program has been selectedr are operat.ive to finish the cooking process by the application of microwave power w.ithout any application of thermal power during a final cooking stage, un-til the sensed temperature drops to a predetermined switch ofE temperature which is lower than the predetermined temperature level and at which the supply of microwave power ceases.
When cooking poultry, the final stage preferably commences lo when the sensed temperature reaches the predetermined level and finishes when the sensed temperature reaches the predetermined switch off temperature. During the final stage the microwave power is preferably increased cornpared with the level of microwave power generated pr.ior to the sensed temperature reaching the predetermined level.
Preferably, the microwave power level is doubled when the 3~
sensed temperature reaches the predetermined level, the supply of thermal power also being discontinued at this point so that no hot air is produced during the final cooking stage.
The temperature sensing means preferably sense the temperature of the hot air flow at a position just downstream of an electric resistance heating element over which the air is recirculated by a fan.
When cooking meats other than poultry, there is preferably an intermediate stage commencing when the sensed temperature reaches the predetermined level and lasting until the sensed temperature 3rops to an intermediate threshold when the final stage commences. During the intermediate stage, the amount of thermal power is preferably reduced, and the amount of microwave power is preferably increased, compared with the respective power levels obtaining prior t~ the sensed temperature reaching the predetermined level.
When cooking poultry items the sensed temperature wlll take longer to reach the predetermined level than for meat items excluding poultry. This time difference can be used to advantage as the temperature/time variation detected by the oven can be used to sense whether the item being cooked is a pouItry item or a meat item other than poultry. If the temperature/time variation indicates that a poultry item is being cooked, when the sensed temperature reaches the predetermined level the oven switches immediately into the final cooking stage during which no hot air is produced. Alternatively, if the temperature/time ~ariation indicates that a meat item other than poultry i9 being cooked, then the oven 3~
commences the intermediate stage when the sensed temperature reaches the predetermined level, and commences the final cooking stage when the sensed temperature reaches the intermediate threshold.
Preferably the oven has the facility to prolong the cooking process for a predetermined proportion of the time occupied by the cooking process, the prolongation being at the levels of microwave power and thermal power prevailing at the switch-off time. Said predetermined proportion may 10 be between 15% and 25%, preferably about 20~.
According to a yet further aspect of the invention there is provided a method of cooking a red meat or poultry item in a microwave oven, comprising commencing with a cavity of the oven in a cold condition, simultaneously applying 15 microwave power and thermal power in the form of a forced flow of hot air through the oven cavity until the hot air temperature reaches a predetermined level, after which the cooking process is finished by the application of microwave power without any thermal power during a final 20 cooking stage, un~il the hot air temperature drops to a predetermined switch-off temperature at which the supply of microwave power ceases.
The invention will now be further described by way of éxample with reference to the accompanying drawings in 25 which: ~
.
Figure 1 is a temperatur'e/time graph showing the variation of hot air temperature with time for a meat item other than poultry cooked ijn a first microwave oven capable of coo~ing in an automatic mode, 3~
Figure 2 i~ a graph corresponding to Figure 1 but showing the temperature/time variation for a poultry item, Fiqure 3 shows the control panel of the second 5 microwave oven capable of cooking in a semi-automatic mode, Figure 4 is a graph showing the temperature/time variations for differing foods cooked in the second microwave oven, Figures 5a and Sb are together a flow chart depicting the cooking process for a baked item of food cooked in the second microwave oven, and Figures 6a to lOa are flow charts depicting the first parts of ~ooking processes of five differing foodstuffs 15 cooked in the second microwave oven.
:
The~ first microwave oven acccrding to the invention is similar to that described in the applicants' European patent application No 0122710 r except that the control means governing the operation of the microwave power and 20 the thermal power are modified so that meats other than poultry are cooked according to the graph of Figure 1 and poultry items are cooked according to the graph of Figure j 2. ~ood items other than meats are cooked in the manner I ~ desoribed in the referenced European patent application.
-25 The Gven has temperature sensing means which comprise a thermistor positioned in the hot air stream just downstream of an~ electric resistance heatinq element. The electric resistance element i5 positioned in a compartment , .
3~
behlnd the back wall of the oven cavity~ as described in the referenced European patent application.
Referring to Figure 1, a meat item other than poultry is subjected to simultaneous microwave power and forced hot 5 air during an initial stage 10 during which the sensed temperature rises steadily with time. When the sensed temperature reaches a predetermined level T1 the m;crowave power level is doubled and the thermal power level is halved for an intermediate stage 12 during which the hot 13 air temperature declines until it reaches a predetermined intermediate threshold temperature level T2. At temperature T2, a final cooking stage 14 commences. During the final cooking stage 14 the microwave power level is maintained at its doubled value but no thermal power is 15 produced. The temperature/time variation therefore drops more steeply during this final cooking stage 14 . When the sensed temperature reaches a predetermined switch off temperature TS, the production of microwave power ceases to mark the end of the cooking process at the time ts.
20 The steepnes of the curve in the final cooking stage 14 provides a precise cut off point at the switch off temperature TS.
During the initial stage 10, the power level may be 200 watts microwave power into the cavity and 1130 watts of 25 hot air, and during the intermediate stage 12 the respective power levels may be 500 and 550 watts. nurin~
the final stage 14, the microwave power level remains at 500 watts but there is no hot air produced. Temperature Tl may be about 2S5QC and ~emperature T2 about 200C.
The temperature~time curve for a poultry item is shown in Figure 2. During the initial stage 10, microwave power and 3~
hot air power are applied simultaneousl~ to the oven cavity until the sensed temperature reaches the predetermined level Tl. This occurs at a time longer than that required for a meat item other than poultry to reach this predetermined temperature level Tl. When ~emperature Tl is reached, the microwave oven switches into its final cooking stage 14 during which the microwave power level is doubled but no hot air is produced. The temperature~ time curve during the final stage 14 therefore drops fairly steeply to provide a precise cut of at the predetermined switch off temperature TS when cooking ceases at time ts.
The power levels during stages 10 and 14 in Figure 2 correspond to the power levels in the stages 10 and 14 in Figure 1.
It will be appreciated that for poultry items and for meat items other than poultry the operation after the sensed temperature has reached the predetermined level Tl is governed by the falling off of the sensed temperature and not by time. As a result of producing no hot air during the final cooking stage 14, the temperature/time curve drops sharply to produce a precise cut off point at the predetermined switch of~ temperature TS.
The first embodiment of microwave oven ls capable of cooking in automatic mode, in that the user does not need to pre-select any particular cooking ~program. The cooking program actually followed in any particular case will be dependent on the temperature/time curve, and in particular the time when the threshold temperature Tl is reached, as described in the aforementioned European patent ~30 appll~catlon.~ ~ ~
Some users prefer to have more control` over the cooking :
3~i process, and the second microwave oven has been developed to meet this need. The second microwave oven is semi-automatic in operation,in that the user pre-selects a program appropriate to the type of food item being cooked, but the manner in which the selected program proceeds is dependent on the temperature/time variation.
Figure 3 shows the control panel of ~he se~ond oven. The panel has a display 20 depicting time and date, together with pads 22 for setting the time and date. Under the lO display 20 are a pad 24 depicted "Automatic Hi-Speed", a pad 26 depicted l'Manual Hi-Speed Turbo" and a pad 28 depicted "Microwave Cook/Defrost". On respective sides are pads 30, 32 marked "Down" and "Up". A large touch pad 34 marked "Start" is provided,and pads 36, 38 marked "Door Open" and "Reset/Off" complete the display panel.
The second oven is again similar in circuit components to that disclosed in the applicants' European patent application published under No 0122710 in that the microwave power i5 delivered to the oven cavity simultaneously with thermal power provided by a circulation of hot air forced through the cavity by a fan.
A temperature sensor in the hot air flow and timing means monitor the temperaturejtime variation. A microprocessor controls the magnitude and duration of the application of the microwave power, and the magnitude and dura~ion of the thermal~power, in~dependence upon temperature/time variatiln.
However, the oven is capable of following a selected one ~of six cooking programs appropriate to the foodstuff being cooked. For example, ie the user wishes to cook a baked foodstuff, eg a pastry item, the pad 24 is touched and ~$~
~ 10 --this causes the microprocessor to control the microwave power and the thermal power so that a cooking procedure appropriate to baked items is followed. The pad 24 is touched a second time if a frozen item is to he defrosted and cooked. The pad 24 is touched a third time if a red meat item is to be cooked, and the pad 24 is touched a fourth time if a poultry item is to be cooked. The pad 24 is touched a fifth time if a complete individual meal is to be cooked, and the pad 24 is touched a sixth time if a 10 pre-cooked food item is to be heated.
Once the pad 24 is touched the number of times appropriate to the foodstuff beir.g cooked, the oven performs the appropriate cooking procedure and terminates the cooking procedure at a switch-off time which will be dependent on 15 the temperature/time variation. If, at switch-off time, the food item is considered not to be cooked the user can again press the "Start" pad 34 which then serves as an 'extra-time' pad and automatically prolongs the cooking procedure for a further 20~ of the cooking time from 20 com~encement of cooking to switch-off time.
Pad 38 is a reset/cancel pad which is operative to cancel any previously selected cooking procedure entered in by pad 24. Pads 30 and 32 (marked "Down" and "Up") enable less well cooked or more well cooked results to be 25 achieved, respectively. For example, if the pad 24 is touched three times to select the red meat cooking progra~
and the pad 30 is touched, the meat item cooked will be rarer than if pad 30 had not ~een touched. Similarly, if pad 32 is touched instead of pad 30 the meat item will be 30 well done.
F~gure 4 shows the tewperature/time variations followed for typical cooking procedures in the second oven. Curve 40 is the temperature/time variation for a typical baked i~em consequent upon touchlrlg of the pad 24 once. The oven automatically switches off when a thrleshold temperature Tl is reached~ which occurs at time C. Curve 42 shows the temperature/time variation for a frozen item which is first defrosted and then cooked, cooking finishing when a predetermined temperature T3 is reached, which occurs at switch off time E. Curve 44 is the temperature/time 10 variation for red meats, cooking finishing at time H.
Curve 46 is the temperature/time variation for poultry, for which cooking finishes at time F. Curve 48 is for items which are being re-heated, which lasts until time A.
Curve 46 results from there being a final cooking stage lS like stage 14 of Figure 2, and curve 44 results fro~ there being an intermediate cooking stage and a final stage, corresponding to stages 12 and 14 of Figure l. It will be noted that curve 44 commences its intermediate stage at a lower temperature than does the curve 46 commence its 20 final stage, this being the only significant difference as between the automatic oven (Figures l and 2) and the semi-automatic oven (Figure 4).
In each case, if extra time is selected after the selected cookîng procedure has been completed r the microprocessor 25 remembers the last mode it was operating in and the overall time taken and automatically programs the oven to cook for a further 20~ of that time. Hence, ifia haked item is cooked and the oven switches off at time C of 20 minutes, subsequent selèctlon of extra time will cause the 30 oven to continue the cooking procedure for a further 4 minutes.
When the pad 24 is touched once, to select a program , ,,,, ,, ,,,_ ,, , ,,, . , .... ..... ..... , . , . . .. -- ---~ ., 3~
appropriate to a baked item, the second microwave oven follows a cooking procedure shown in the flow chart of Figures 5a and 5b. The part of the procedure shown at S0 is the selection of the 'baked' program, with the option for lightly baked or well baked, and the starting of cooking by touching the pad 340 If the temperature (as detected by the thermistor in the rear compartment~ is above 80C, automatic cool down of the oven cavity is achieved by directing cooling air through the oven cavity from the magne~ron blower and the convection blower, as indicated at 52.
As cooking proceedsr the total cooking time is monitored (54) and the display 20 shows the program selected and whether the Down or Up pad was touched. When the threshold temperature Tl is reached, the production of microwave power and convection power ceases ~56~, and the display 20 then shows "Cooking Complete" (58).
After the oven door has been opened, the display 20 invites the user to select the option of extra time. If this is required, the user again presses the start pad 34 (as indicated at 59j, and the oven automatically continues both microwave power and thermal power, at the levels prevailing immediately before switch off, for a further time equal to 20% of the time from commencement o~ cooking to switch Off-Yet further extra time may be selected (69) if the userwishes.
' During any extra time cooking, the display 20 shows 20% of the cooking time as monitored at 54, and the timer counts 30 ~own to ~ero.
, Figure 6a corresponds to Figure 5a, but shows the flow chart appropriate to the p~ogram for frozen foods. The remainder of the program for frozen foods is identical to that for baked items, so Figure 6a should be combined with 5 Figure 5b for the complete flow chart for frozen food items.
Similarly, Figure 7a corresponds to Figure 5a, but shows the flow chart appropriate to roast meats. It will be seen that the program has stages 1, 2 and 3 corresponding to 10 the curve 44 of Figure 4. The remainder of the program for roast meats is identical to that for baked items, so Figure 7a should be combined with Figure 5b for the complete flow chart for roast meat items.
Figure 8a corresponds to Figure 5a, but shows the flow 15 chart appropriate to poultry. It will be seen that the program has stages 1 and 3, corresponding to the curve 46 of Figure 4. The remainder of the program for poultry i5 identical to that for baked items. So Figure 8a should be combined with Figure 5b for the complete flow chart for 20 poaltry items.
Figures 9a and lOa correspond to Figure 5a, but show the flow charts appropriate to cooking complete individual meals and heating pre-cooked foo~s, respectively.
Claims (8)
1. A microwave oven comprising a microwave generator for supplying microwave power to a cavity of the oven, thermal heating means for supplying thermal power in the form of a forced flow of hot air through the cavity, memory means storing a first cooking program appropriate to a baked item, a second cooking program appropriate to a meat joint other than poultry, and a third cooking program appropriate to poultry, selector means for selecting one of said first, second and third cooking programs, temperature sensing means for sensing the temperature of the hot air flow, and control means which are responsive to the selector means and the temperature sensing means and which, when the sensed temperature reaches a predeter-mined level due to the simultaneous generation of microwave power and thermal power, are operative either to switch off the supply of power to the microwave generator and the thermal heating means and thereby finish the cooking process if the first program has been selected, or if the second or third program has been selected, are operative to finish the cooking process by the application of micro-wave power without any application of thermal power during a final cooking stage, until the sensed temperature drops to a predetermined switch off temperature which is lower than the predetermined temperature level and at which the supply of microwave power ceases.
2. A microwave oven according to claim 1, wherein the final stage commences when the sensed temperature reaches the predetermined level and finishes when the sensed temperature reaches the predetermined switch off temperature.
3. A microwave oven according to claim 1, wherein during the final stage the microwave power is increased compared with the level of microwave power generated prior to the sensed temperature reaching the predetermined level.
4. A microwave oven according to claim 3, wherein the microwave power level is doubled when the sensed temperature reaches the predetermined level, the supply of thermal power then being discontinued so that no thermal power is produced during the final cooking stage.
5. A microwave oven according to claim 1, wherein there is an intermediate stage commencing when the sensed temperature reaches the predetermined level and lasting until the sensed temperature drops to an intermediate threshold when the final stage commences.
6. A microwave oven according to claim 5, wherein during the intermediate stage, the amount of thermal power is reduced, and the amount of microwave power is increased, compared with the respective power levels obtaining prior to the sensed temperature reaching the predetermined level.
7. A microwave oven according to claim 1, wherein the oven comprises means for prolonging the cooking for a predetermined proportion of the time occupied by the cooking process to switch-off time, to provide a prolongation of the cooking time beyond the switch-off time, the prolongation being at the levels of microwave power and thermal power prevailing at the switch-off time.
8. A microwave oven according to claim 7, wherein the predetermined prolongation proportion is substantially between 15% and 25% of the time occupied by the cooking process to switch-off time.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB858500096A GB8500096D0 (en) | 1985-01-03 | 1985-01-03 | Microwave ovens |
| GB8500096 | 1985-01-03 | ||
| GB8502571 | 1985-02-01 | ||
| GB858502571A GB8502571D0 (en) | 1985-02-01 | 1985-02-01 | Microwave ovens |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249036A true CA1249036A (en) | 1989-01-17 |
Family
ID=26288632
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000498944A Expired CA1249036A (en) | 1985-01-02 | 1986-01-03 | Microwave ovens and methods of cooking food |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4661670A (en) |
| EP (1) | EP0187543A3 (en) |
| AU (1) | AU573412B2 (en) |
| CA (1) | CA1249036A (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0239290B1 (en) * | 1986-03-26 | 1991-12-11 | Microwave Ovens Limited | Microwave ovens and methods of cooking food |
| GB8613552D0 (en) * | 1986-06-04 | 1986-07-09 | Microwave Ovens Ltd | Microwave ovens |
| GB8613553D0 (en) * | 1986-06-04 | 1986-07-09 | Microwave Ovens Ltd | Microwave ovens |
| GB2202117B (en) * | 1987-03-10 | 1990-05-16 | Ti New World Ltd | Microwave ovens |
| US4970359A (en) * | 1987-09-30 | 1990-11-13 | Ki Tae Oh | Automatic cooking control systems for a microwave oven |
| KR900002206B1 (en) * | 1987-10-13 | 1990-04-04 | 주식회사 금성사 | Automatic cooking method for microwave range |
| KR900003965B1 (en) * | 1987-12-22 | 1990-06-05 | 주식회사 금성사 | Cooking method of electronic range |
| KR900003967B1 (en) * | 1987-12-22 | 1990-06-05 | 주식회사 금성사 | Cooking method of electronic range |
| GB8802575D0 (en) * | 1988-02-05 | 1988-03-02 | Microwave Ovens Ltd | Microwave ovens & methods of defrosting food therein |
| US5109956A (en) * | 1989-05-26 | 1992-05-05 | Nunzio's Pizza, Inc. | Food preparation and delivery apparatus and method |
| GB9209350D0 (en) * | 1992-04-30 | 1992-06-17 | Microwave Ovens Ltd | Microwave ovens and methods of cooking food |
| KR0168177B1 (en) * | 1995-02-28 | 1999-01-15 | 김광호 | Temperature control method & device of microwave oven |
| US5698123A (en) * | 1996-01-16 | 1997-12-16 | Black & Decker Inc. | Toaster compensation for repeated use |
| US6525301B1 (en) * | 1999-01-13 | 2003-02-25 | General Electric Company | Combination oven with manual entry of control algorithms |
| US6403937B1 (en) * | 2000-07-08 | 2002-06-11 | The Garland Group | Combination convection/microwave oven controller |
| US6987252B2 (en) | 2001-01-11 | 2006-01-17 | General Electric Company | Speedcooking oven including convection/bake mode and microwave heating |
| US6462319B1 (en) | 2001-05-29 | 2002-10-08 | Bsh Home Appliances Corporation | Multi-stage self-cleaning control for oven |
| US7461588B2 (en) * | 2004-08-31 | 2008-12-09 | General Electric Company | Methods and apparatus for operating a speedcooking oven |
| BE1017073A3 (en) * | 2005-06-23 | 2008-02-05 | Wautelet Philippe | Method of radiation controlled materials by artificial intelligence. |
| ES2320076B2 (en) * | 2007-07-11 | 2010-01-26 | La Morella Nuts, S.A. | CONTINUOUS PROCEDURE FOR MANUFACTURING FOOD PRODUCTS. |
| US9402284B1 (en) * | 2009-10-08 | 2016-07-26 | Spring (U.S.A.) Corporation | Reconfigurable induction cooktops |
| CN108720583B (en) * | 2017-04-17 | 2021-09-24 | 浙江绍兴苏泊尔生活电器有限公司 | Cooking appliance and control method thereof |
| US11412584B2 (en) | 2017-12-08 | 2022-08-09 | Alkar-Rapidpak, Inc. | Ovens with metallic belts and microwave launch box assemblies for processing food products |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB113467A (en) * | 1917-02-17 | 1918-02-18 | Serge Vincent De Bolotoff | Improvements in or relating to Means to Receive Strut-ends in Aeroplanes and other Structures. |
| JPS54102639A (en) * | 1978-01-30 | 1979-08-13 | Matsushita Electric Ind Co Ltd | High frequency heating device |
| JPS592802B2 (en) * | 1978-09-25 | 1984-01-20 | シャープ株式会社 | heating cooker |
| JPS55119391A (en) * | 1979-03-06 | 1980-09-13 | Sharp Kk | Cooking oven |
| GB2127658B (en) * | 1982-07-17 | 1986-01-29 | Microwave Ovens Ltd | Microwave ovens and methods of cooking food |
| GB8307123D0 (en) * | 1983-03-15 | 1983-04-20 | Microwave Ovens Ltd | Microwave ovens |
| US4582971A (en) * | 1984-02-07 | 1986-04-15 | Matshushita Electric Industrial Co., Ltd. | Automatic high-frequency heating apparatus |
-
1985
- 1985-12-31 EP EP85309549A patent/EP0187543A3/en not_active Withdrawn
-
1986
- 1986-01-02 AU AU51781/86A patent/AU573412B2/en not_active Ceased
- 1986-01-02 US US06/815,531 patent/US4661670A/en not_active Expired - Fee Related
- 1986-01-03 CA CA000498944A patent/CA1249036A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0187543A3 (en) | 1988-03-30 |
| US4661670A (en) | 1987-04-28 |
| EP0187543A2 (en) | 1986-07-16 |
| AU573412B2 (en) | 1988-06-09 |
| AU5178186A (en) | 1986-07-10 |
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